"Friends Only" Plug-in will not deactivate

I’m using 3.5.1, Twentytwelve child theme.

I’ve been using “Friends Only” plugin to have some reviewers look at my site before I go live in public. Worked great.

But when I deactivated it today, this deactivation was confirmed but it is still active.

I turned on my “Ultimate Coming Soon Page” plug-in to work the reviewers comments into my site privately. The Ultimate Coming Soon Page works, but the Friends Only plug-in, even though it is deactivated (and I deleted all of the permitted e-mail addresses)is still active, and comes up first, then when logged in on its entry page, the Ultimate Coming Soon Page appears next.

I emptied cache, logged out and in, refreshed, etc.

How do I get rid of Friends Only plug-in activity?

I deleted the plug-in itself. But still the “please enter your log-in address with a “box” comes up when I browse to my web-site as a non-admin person.

It seems that the plug-in did changed something in my core (child) theme, somewhere, (or in the parent?) — it’s a mystery to me…….

Help would be very much appreciated.